1. Field of the Invention
The invention relates to a damper means for a shock absorber which damper means comprises a damper-fluid filled piston and cylinder arrangement, an auxiliary tank, and a flow channel between the two. More specifically, the invention relates to such a damper means including variable high damper-fluid flow speed restriction means and variable low damper-fluid flow speed restriction means in the flow channel, and a variable high damper-fluid flow speed restriction means and a variable low damper-fluid flow speed restriction means in the piston and cylinder arrangement.
2. Description of Prior Art
Known in the art are damper means comprising oil-filled or damper-fluid filled piston and cylinder arrangements with auxiliary tanks as illustrated in, for example, U.S. Pat. No. 4,546,959, Tanno, Oct. 15, 1985, U.S. Pat. No. 4,706,787, Wossner, Nov. 17, 1987, and U.S. Pat. No. 4,159,106, Nyman, June 26, 1979. The Tanno patent teaches the use of a variable restriction in the flow channel between the piston and cylinder arrangement and the auxiliary tank, but it is a single variable restriction and therefore has a limited range of adjustment. In addition, Tanno teaches a fixed restriction and a possibly variable restriction associated with the piston and cylinder arrangement.
The Wossner patent also teaches a damper arrangement of the same general class. However, the variable restrictions in the piston and cylinder arrangement of Wossner is disposed in serial arrangement, and Wossner does not teach any restrictions between the piston and cylinder arrangement and the auxiliary tank.
Nyman teaches a single variable restriction in the flow channel, and the possibility of a single variable restriction associated with the piston and cylinder arrangement.
U.S. Pat. No. 4,442,926, Muto, Apr. 17, 1984, also teaches a damper comprising a damperfluid filled piston and cylinder arrangement, and an auxiliary tank. Variable restrictions, for the compression and extension strokes, are included in the piston and cylinder arrangements.
The problems with the above available dampers, and others not identified herein, is that they have a limited range of adjustment and, typically, except for Tanno and Wossner, the adjustments cannot be made externally, so that they comprise in fact factory, rather than user, adjustments.
In addition, and especially in dampers as in the Tanno patent, there is a danger of cavitation, the so-called meter-out effect, behind the piston (on the rod side thereof) during the compression stroke.